Are clustering effects accounted for in statistical analysis in leading dental specialty journals?

Fleming, Padhraig S; Koletsi, Despina; Polychronopoulou, Argy; Eliades, Theodore; Pandis, Nikolaos (2013). Are clustering effects accounted for in statistical analysis in leading dental specialty journals? Journal of dentistry, 41(3), pp. 265-70. Elsevier Science 10.1016/j.jdent.2012.11.012

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OBJECTIVES In dental research multiple site observations within patients or taken at various time intervals are commonplace. These clustered observations are not independent; statistical analysis should be amended accordingly. This study aimed to assess whether adjustment for clustering effects during statistical analysis was undertaken in five specialty dental journals. METHODS Thirty recent consecutive issues of Orthodontics (OJ), Periodontology (PJ), Endodontology (EJ), Maxillofacial (MJ) and Paediatric Dentristry (PDJ) journals were hand searched. Articles requiring adjustment accounting for clustering effects were identified and statistical techniques used were scrutinized. RESULTS Of 559 studies considered to have inherent clustering effects, adjustment for this was made in the statistical analysis in 223 (39.1%). Studies published in the Periodontology specialty accounted for clustering effects in the statistical analysis more often than articles published in other journals (OJ vs. PJ: OR=0.21, 95% CI: 0.12, 0.37, p<0.001; MJ vs. PJ: OR=0.02, 95% CI: 0.00, 0.07, p<0.001; PDJ vs. PJ: OR=0.14, 95% CI: 0.07, 0.28, p<0.001; EJ vs. PJ: OR=0.11, 95% CI: 0.06, 0.22, p<0.001). A positive correlation was found between increasing prevalence of clustering effects in individual specialty journals and correct statistical handling of clustering (r=0.89). CONCLUSIONS The majority of studies in 5 dental specialty journals (60.9%) examined failed to account for clustering effects in statistical analysis where indicated, raising the possibility of inappropriate decreases in p-values and the risk of inappropriate inferences.

Item Type:

Journal Article (Original Article)


04 Faculty of Medicine > School of Dental Medicine > Department of Orthodontics

UniBE Contributor:

Eliades, Theodore and Pandis, Nikolaos


600 Technology > 610 Medicine & health




Elsevier Science




Eveline Carmen Schuler

Date Deposited:

14 Feb 2014 16:26

Last Modified:

24 Apr 2017 15:20

Publisher DOI:


PubMed ID:



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